A composite mixture, such as a mortar or a concrete, comprising a powder, a granular material (a fine aggregate), a massive material (a coarse aggregate) and a liquid, such as water, has widely been used for various engineering work and constructions. For preparing the mixture, it is a common practice to adopt, in absolute dry condition, a water absorption, Q, according to JIS for granular and massive materials and a specific density (.rho.SD) for a fine aggregate and to determine a design of mix proportion by a statical method in line with a given purpose. It is substantially true of the case where additives and fibrous materials are properly added.
However, as is well known, when the above-described preparation is conducted, there occur problems, such as adsorption phenomenon (or dispersion phenomenon) of the above-described powder and granule in the presence of a liquid, which makes it impossible to prepare a well-proportioned product. The above-described adsorption phenomenon (dispersion phenomenon) has an effect on the moldability or compactability, or susceptibility to bleeding or separation when an intended product is prepared through the use of the mixture, or on the strength or other properties of products after hardening of the kneaded product, as well as on the transportation and handling.
For this reason, some studies have been made on the above-described adsorption phenomenon etc. In the prior art, however, the above-described phenomenon etc. are understood merely from the theoretical and qualitative viewpoints. Under the above-described state of the art, the present inventors have previously made proposals disclosed in Japanese Patent Application No. 5216/1983 (corres. to JP, A No. 59-131164) and Japanese Patent Application No. 245233/1983 (corres. to JP, A No. 60-139407), and particularly proposed a series of method on a test for quantification of the adsorbed liquid on the surface of the fine aggregate used for the concrete or mortar, or on the preparation of a kneaded product wherein the test results are utilized. Specifically, in the above-described prior art, observation is made on the above-described liquid, such as water attached to the surface of the grain or powder, through classification into (a) one retained through a capillary phenomenon between particulate materials and (b) one adsorbed on the surface of particulate materials. In particular, an attempt has been made on the quantitative determination of the latter. Further, it is possible to efficiently conduct measurements of a plurality of samples under the same centrifugal condition, which enables the liquid components desultorily understood and grasped as the same liquid in the art to be each understood through classification and further the results of measurements to be quantified according to the respective conditions, so that a marked improvement in the kneading and preparation can be attained.
The amount or percentage of water absorbed in the fine aggregate in preparing the above-described mixture has hitherto been taken into consideration to some extent and prescribed also in JIS A1109 as a percentage of water absorption Q through the use of an equation.
In such a mixture, the fluidity apparently has an important effect on the moldability or compactability, and regarding the measurement of the fluidity, the measurement of the flow value is prescribed in JIS R5201 as a physical testing method for cement. Specifically, the fluidity of the above-described mixture is determined as its developed diameter on a flow table.
The above-described conventional general technique relates to a fine aggregate as specified in JIS, and though the liquid components of the above-described kneaded product or the like are evaluated and controlled through the use of measured values, such as percentage of water absorption, finess modulus and solid volume percentage, in a saturated surface-dry condition, physical properties of a specific kneaded product cannot properly be evaluated and controlled. Specifically, as is well known, for the above-described kneaded product, it is necessary to have information on properties such as susceptibility to separation and bleeding or workability, pumpability and compactibility. The above-described properties of the resultant mixture vary even when the water to cement ratio and sand to cement ratio are the same. In order to solidly pack and mold the kneaded product, it is a common practice to conduct a consolidation treatment such as vibration. In most cases, the behavior and change which the kneaded products show during the vibration or other consolidation treatment are remarkably different from each other even when the same measured values are obtained by the method prescribed in JIS. The properties of a ready-mixed concrete or mortar varies when a concrete is placed in a large thickness, or in a vertical form work a concrete is placed and packed therein.
The present inventors have proposed an advantageous method which comprises dividing mixing water for kneading, uniformly adhering part of the mixing water in a particular amount range to a fine aggregate, adding cement thereto for primary kneading, and adding the remaining water for secondary kneading, thereby preparing a mixture less susceptible to bleeding and separation and having excellent workability and capable of considerably enhancing the strength and other properties under the same mix proportion. This method had enjoyed a good reputation in the industry. However, even when the above-described method is employed, the degree of the above-described various effects on the resultant kneaded product vary if the fine aggregate is different.
The above-described prior art method proposed by the present inventors for the purpose of solving the above-described problem is very useful because not only is the liquid component classified into one adsorbed on the surface of the particle and one not adsorbed on the surface of the particle but also the adsorbed liquid is quantitatively determined. However, detailed studies on the data wherein specific measurements are made on the above-described technique and concrete and mortar are prepared based on the results have revealed that there is a tendency that the expected properties for the mortar and concrete cannot be obtained precisely. Specifically, according to the experimental results, it is not easy to ensure the control of the mutual intervention between an aggregate, such as a fine aggregate, and a powder (compatibility between the aggregate and the cement) and the aggregate (including a fine aggregate). It is expected that the surface roughness, shape, water retainability, of these materials, i.e., qualities of the aggregate unable to be elucidated by the conventional method prescribed in JIS greatly take part in the susceptibility to separation and bleeding, workability, pumpability and compactability of the concrete and mortar. In the above-described method, such a relationship cannot properly be elucidated, and a kneaded product cannot be efficiently prepared.
Accordingly, in practice, as is described in various literature on the execution of work of concrete etc., trial mixing is repeated to determine the most advantageously mixing-kneading condition possible. However, the trial mixing needs a considerable number of steps and time. For example, when determination of conditions including the strength of the resultant product is intended, it generally takes a period of time as long as four weeks. Therefore, when the trial mixing and test are repeated, a remarkably long period of time is spent, which renders this method unsuitable for actual execution of work. This forces the whole to be fundamentally estimated from the trial mixing etc. through experience or perception of individual workers, or tests of items capable of obtaining the results in a relatively short period of time. This lacks the rationality and cannot provide a proper consistency, which make it necessary to expect a considerably wide error range. The percentage of water absorption prescribed in JIS has some grounds to rely on, and specific amount of mixing water or the like is determined by taking the percentage of water absorption into consideration. However, as is well known in the art, the conventional method wherein the conventional percentage of water absorption prescribed in JIS is substracted or added to determine the amount of mixing water does not always provide a kneaded product or final product having predetermined properties. In the art, the occurrence of such a variation is understood as an unavoidable phenomenon caused by the adoption of the naturally obtained sand etc.
It is a matter of course that the flow value for measuring the fluidity or moldability of the mixture has some grounds to rely on. However, it is difficult to elucidate the value obtained by the development diameter of a kneaded product on a flow table. For example, even when the relationship with the water to cement ratio being an apparent deciding factor of the flow value is diagramed, no curve can be obtained on a rectangular coordinate, so that it is very difficult to conduct an analysis based on the results.